Strange model View, like

[Naish]

Ha, OK, now I know more about CLIPPING . I wish I would never have met it.
In my case the

@Naish

Terrain Context data from “digital globe”

that I added to my drawing was too spacious.
removing it did not bring the model back to its previous state, but improved the Situation.

I think, it will never disappear from Sketchup, but maybe it will get better:

@colin

It’s the kind of thing you would hope we will fix soon.